# NCERT Solutions for Class 8 Science Chapter 12 Friction

NCERT Solutions for Class 8 Science Chapter 12 Friction will help in developing a wide range of knowledge when you’re brainstorming solutions. Students can easily review the answers they prepared and also know whether they learned it properly or not.

Chapter 12 CBSE Class 8 Science NCERT Solutions will provide a lot of relevant content, making you well versed in variety of topics and able to easily recall your ideas. These can be used to help you remember the details of any question.

## Chapter 12 Friction Class 8 Science NCERT Solutions

### Exercise

1. Fill in the blanks.
(a) Friction opposes the ______ between the surfaces in contact with each other.
(b) Friction depends on ______ of the surfaces.
(c) Friction produces ______.
(d) Sprinkling of powder on the carom board ______ friction.
(e) Sliding friction is ______ than the static friction.

Solution

(a) relative motion
(b) nature
(c) heat
(d) decreases
(e) less

2. Four children were asked to arrange forces due to rolling, static and sliding frictions in decreasing order. Their arrangements are given below. Choose the correct arrangement.
(a) Rolling, static, sliding
(b) Rolling, sliding, static
(c) Static, sliding, rolling
(d) Sliding, static, rolling

Solution

(c) Static, sliding, rolling

3. Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be:
(a) Wet marble floor, dry marble floor, newspaper and towel.
(b) Newspaper, towel, dry marble floor, wet marble floor.
(c) Towel, newspaper, dry marble floor, wet marble floor.
(d) Wet marble floor, dry marble floor, towel, newspaper.

Solution

(a) Wet marble floor, dry marble floor, newspaper and towel.

4. Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

Solution

The frictional force acting on it is in the upward direction.

5. You spill a bucket of soapy water on a marble floor accidently. Would it make easier or more difficult for you to walk on the floor? Why?

Solution

The slippery nature of soapy water will make it more difficult to walk across. It also creates a smooth surface since it contains no irregularities.

6. Explain why sportsmen use shoes with spikes.

Solution

Sportsmen use shoes with spikes to get a better grip on the ground. Spikes act as irregularities and help in increasing friction.

7. Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force and why?

Solution

Seema will experience more frictional force since the heavier box applies greater pressure on the floor as compared to the lighter box.

8. Explain why sliding friction is less than static friction.

Solution

An irregularity on the two surfaces that are locked into one another is more responsible for the force acting between two surfaces at rest. When a body moves or slides, the contact points do not get enough time to lock into one another. Thus, sliding friction is always lower than static friction.

9. Give examples to show that friction is both a friend and a foe.

Solution

Friction is a friend :
(i) We are able to move on road.
(ii) We are able to write on board with chalk.
(iii) We are able to fix a nail in the wall.
Friction is considered a foe.
(i) Things experience wear and tear.
(ii) Heat is produced in machines which damages its parts.
(iii) The speed of the vehicle reduces due to friction.

10. Explain why objects moving in fluids must have special shapes.

Solution

It is necessary for objects to overcome friction acting on them when moving through fluids. In this process, energy is lost. As a result, special shapes are given to the objects in order to minimize friction.